By the looks of things, yes. But Nexus Destruction can be very powerful and disruptive. Dropping a card you don't need and exhausting a spirit you don't plan on attacking or blocking with is often well worth destroying that annoying roadblock in your way.

Yes, you have to exhaust the spirit. But the ability on the card doesn't discard from the opponent's hand. YOU are the one who discards a card. What it does is destroy a nexus that the opponent controls. Because of this, I believe that the cost is fair. So what actually happens is that you exhaust the spirit as well as discarding a card, but you can destroy a nexus that is causing you problems.